The present invention relates to a process for pneumatic holding of yarn spun from fibers under different work conditions as well to a device to carry out this process.
In textile machines, in particular in spinning machines such as open-end spinning machines, it is customary to hold a yarn by means of suction air (DE 23 50 843 A1) to carry out a given work phase. For example, the yarn is cut, merely stored, or transferred from one position to another during this work phase. In this process, the problem occurs, however, that the end of the pneumatically held yarn is affected by the air stream and therefore less than perfect quality is available for the subsequent work steps, so that errors in work or even interruption of the work process may result.
It is the principal object of the present invention to create a process and a device by means of which excessive stress on and thereby damage to the yarn end, and thus a disturbance of the work process resulting from such damage, may be avoided. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
This principal object is attained by the invention through adapting the intensity of the air stream holding the yarn to the prevailing work conditions. Due to the fact that the intensity of the airflow brought to bear upon the yarn is adapted to the current operating conditions, the lowest possible intensity of the air stream can be selected for this purpose. The yarn is treated with care in the time interval during which it is exposed to the air stream, while the intensity of the air stream remains strong enough to carry out its task reliably.
The term xe2x80x9cworking conditionsxe2x80x9d is not only to be understood in the sense of the present invention to relate to the work phases following the pneumatic holding of the yarn, but also relates to the different yarn characteristics with regard to yarn thickness, fiber material spun into the yarn and yarn structure as well as yarn twist, fiber incorporation, etc.
The working conditions may be different depending on the textile conditions and/or the operating position. Therefore, it is possible according to an advantageous embodiment of the process to change the intensity of the air stream brought to bear on the yarn end in work phases following each other in time and in adaptation to the task to be accomplished in that case. This change of intensity allows secure handling of the yarn with the least possible flow intensity in an optimal manner.
Complementing or as an alternative to, an adaptation of the flow intensity to different work phases, it is an advantageous to adapt the air stream acting upon the yarn end to the character of the yarn. The xe2x80x9ccharacter of the yarnxe2x80x9d in this case should be understood to be the yarn thickness, the fiber material spun into the yarn, the twist of the yarn or its structure, etc., which may show considerable differences, depending on the spinning process used.
According to the invention, the air stream for the reception of a yarn is set at a high intensity, since the task to be accomplished as a rule consists of releasing the yarn from the influence zone of another element in which it is held by that element. In addition, the air stream does not necessarily act upon the end of such a yarn to be accepted, but in some cases upon a middle area of the yarn, so that the latter must be taken up in form of a loop. For this process, an intensive air stream is useful.
In a further development according to the invention of the described process, the yarn to be cut is held under tension by an air stream of high intensity, so that the cutting point is accordingly determined very precisely as related to the yarn to be cut.
If the task consists merely in holding the yarn after cutting, the intensity is maintained advantageously only until the severed yarn end has been removed. The intensity is then reduced to a value sufficient for the yarn end formed by the cutting process to be held securely on the one hand, while, on the other hand, it is exposed to the lowest possible air stream so that the yarn end may not be frayed and may essentially preserve its character. In an advantageous further development of the process according to the invention, such a reduction of the air stream intensity is effected before the yarn is taken out of the range of influence of the air stream. This reduction occurs whether or not the yarn was to be cut in the pipe in which it had been held previously.
In order to reduce the air stream acting upon the yarn, a secondary air stream can be fed to this air stream outside the area in which the yarn is located.
In another advantageous variation of the described process, the cross-section of a line conveying the yarn and the air stream can be changed to control the intensity of the air stream acting upon the yarn.
To carry out the process, a device for pneumatic holding of a yarn by means of a line connected to an air source is used. Thanks to the air control device according to the invention it is possible to control the air stream which can be brought to bear upon the yarn in such manner that it is as weak as possible on the one hand, while on the other hand it is strong enough that it securely holds the yarn as required by the current operating conditions in an optimal manner.
The air control device can be designed in different ways. Thus, it is possible to design the air control device of the object of the invention in an advantageous manner using control openings or chokes. Beyond this, it is possible with the design of the air control device of the invention to actuate one or several intermediate positions in addition to the two end positions that can also be adjustable. In that case, it is advantageous to provide a monitoring device to adapt the intensity of the airflow to different yarn thicknesses.
In addition, a yarn severing device can be assigned to the air control device and, if applicable, can be an integral part of the air control device.
The process and the device according to the invention make it possible in a simple and optimal manner to hold the yarn carefully. The process and the device are based on the realization that, in adapting the air stream to different operating conditions, it is possible to hold the yarn securely, depending on the prevailing operating conditions, when the intensity of the airflow is as strong as possible as well as when it is reduced. This not only results in a careful treatment of the yarn but, depending on the design of the air control device, also in savings in energy, since the air source need provide less air for certain operating conditions than for other operating conditions.